Detector for particulate matter in flowing gas streams

ABSTRACT

Apparatus is an air-cooled and air-cleaned photoelectric smoke or particulate matter detector that can be installed into a gas flue or other gas passageway using only one entry into the flue through a single aperture.

United States Patent [19 1 Prellwitz DETECTOR FOR PARTICULATE MATTER IN FLOWING GAS STREAMS [75-] Inventor: Samuel B. Prellwitz, Pittsburgh, Pa.

[73] Assignees United States Steel Corporation, Pittsburgh, Pa.

[22] Filed: 0ct.20, 1972 [21] Appl. No.: 299,534

[52] US. Cl ..250/575, 340/237, 356/207 [51] Int. Cl. G01n21/26 [58] Field of Search 356/206, 207, 208; 250/218, 227; 340/237 [56] References Cited UNITED STATES PATENTS 6/1950 Hobelmann ..250/218 9/1947 MacAdams 356/206 [4s] May 7, 1974- 1,785,392 12/1930 Sawford 340/237 S 2,791,932 5/1957 Ha1l 356/206 2,854,585 9/1958 Simmons.. 250/218 2,394,129 2/1946 West 356/206 3,417,250 12/1968 Kadivnik 250/218 2,324,304 7/1943 Katzman 356/206 3,628,028 12/1971 Thorsheim... 250/218 3,564,272 2/1971 Payton 356/207 Primary ExaminerJames W. Lawrence Assistant Examiner-D. C. Nelms Attorney, Agent, or Firm-Donald S. Ferito [5 7] ABSTRACT Apparatus is an air-cooledand air-cleaned photoelectric smoke or particulate matter detector that can be installed into a gas flue or other gas passageway using only one entry into the flue through a single aperture.

4 Claims, 1 Drawing Figure DETECTOR FOR PARTICULATE MATTER IN FLOWING GAS STREAMS air cleaning equipment, etc.

A well-known method for accomplishing such detection has been through the use of a source of light and a photocell. In the practice of this method, the light source is locatedon one side of a gas stream and the photocell is located diametrally opposite the light' on the other side of the gas stream. More or less light is obscured as more or less particulate matter passes in the gas stream through the beam between the light source and the photocell.

Prior to my invention, serious disadvantages were en countered in using the above-described photoelectric method in that apertures had to be made in each of two opposite walls of the passageway through which the gas stream flowed. In many instances, it is impractical or impossible to make the two apertures; the walls of the passageway may be excessively thick masonry as, for example, the smoke stack of a coke oven battery; or only one side of the passageway may be accessible as in an underground-flue where the entry may be made practically only from the top surface. The installation ofmuch combustion equipment is made with under ground flues and is supplied usually with occasional manholes for inspection and cleaning purposes. These manholes provide convenient access to the flue.

My invention comprises a photoelectric smoke or particulate matter detector that accomplishes its purpose using only one entry into a gas passageway through a single aperture. This makes it applicable to many installations where, prior to my invention, it was impossible to utilize a photoelectric smoke or particulate matter detection system.

lt is, accordingly, the primary object of my invention to provide an improved photoelectric smoke or particulate matter detecting apparatus which can be installed and operated through a single aperture in a gas passageway.

his a more specific object of my invention to provide an improved photoelectric system as set forth in the above statement of object which includes a unitary housing containing a pair of photoelectric cells; a light source for the photoelectric cells; means sealing the beam from the light source to one of the photoelectric cells and exposing the beam from the light source to the other photoelectric cell through the gas stream traveling through a passageway in which the housing is installed; and means connected with the photoelectric cells for indicating differences in intensities of the light traveling from the light source to the two photoelectric cells so that the density of or the amount of particulate matter in the gas stream traveling through the passageway can be determined.

It is another object of my invention to provide an improved photoelectric detecting apparatus as set forth by the object immediately above which includes means for circulating ambient air through the housing for cooling and cleaning purposes.

The above and other objects will become more apparent after referring to the following specification and drawing in which the single FIGURE is a longitudinal sectional view showing the apparatus of the invention installed in a gas passageway.

Referring now more particularly to the drawing, reference numeral 2 designates generally the wall ofa flue 3 having an aperture or opening 4 therethrough. The

Y apparatus of the invention, designated generally by reference numeral 6, is shown inserted into the flue through the aperture 4. The aperture is sealed by a cover plate 8 which surrounds the apparatus of the invention and is shaped to receive the apparatus. The apparatus 6 includes an elongated housing 10 having a first compartment 12 formed on the end thereof adapted to be inserted into the flue and a second compartment 14 formed on the end thereof which projects outwardly of the flue when the apparatus 6 is inserted therein. r

The housing 10 is provided with a substantially L- shape duct 16 connecting the compartments 12 and 14. Duct 16 is provided with an open-end short leg portion 18 which extends ouwardly of the compartment 12 substantially parallel with the long leg portion 20 of the duct 16. A second substantially L-shape duct 22 surrounds duct 16. Duct 16 is sealed from duct 22 and is located therewithin in a concentric manner.

A third duct 24 having an open end 26 extends from the compartment 14 through the cover plate 8 and the flue wall 2. The open end 26 of the duct 24 is spaced from and in alignment with the open end of the end portion 18 of duct 16.

Light from alight source in the form of a lamp 28 disposed in the compartment 12 is collimated by two lenses 30a and 30b which are disposed one on opposite sides of the lamp 28 in the compartment 12. The lenses collimate the light from the lamp 28 so that one beam of light proceeds through lens 30a to a plane mirror 32 and thence upward through the short end portion 18 of duct 16. The beam oflight which is directed by the lens 30a to the mirror 32 eventually falls upon a photoresistive light detector or electrophotocell 34 mounted in the compartment 14 located outside of the flue wall 2. Another beam of light passes through lens 30b, strikes plane mirror 36 and is directed upwardly through the long leg portion 20 of duct 16 until it strikes another electroresistive light detector or photoelectric cell 38 which is also mounted in the compartment 14 outside of the flue wall 2.

The compartment 12 is disposed in the end of the duct 16 between the long leg portion 20 and the short leg portion 18.

Duct 22 is provided with apertures 40 at the end outside the flue walls 2 to permit free flow of ambient air into the duct 22, down around duct 16 and the compartment l2, and eventually out into the gas stream flowing through the gas flue 3 via an opening 42 adjacent the end of the duct 22 which surroundsthe compartment l2.

Compartment 14 is open at its outer end, but the opening is fitted with a fiber glassfilter 44 similar in construction to furnace filter, stock number 8314 supplied by Sears, Roebuck and Company. The compartment 14 and its filter 44 are covered by a loosely fitting cover 46 in such a manner that air may flow freely between the cover and the compartment 14, passing through the'filter 44 on the way. The compartment 14 and ducts l6 and 22 are contiguous and, as indicated by arrows, there is free passage of ambient air from the compartment 14 through ducts l6 and 24 into the flue 3 whose smoke or particulate matter content is being measured. Cooling ambient air flows into the openings 40 of duct 22, through the duct and then outwardly into the gas stream in the flue through opening 42.

The lamp ,8 may be fl c al El tr ...N. 1,15 bulb, and lenses 30a and 3012 are simple double convex or asymmetric collimating lenses of diameter and focal length suited to the dimensions of a particular size detector. Mirrors 32 and 36 are simple, plane glass, silvered mirrors mounted on a support 48 that holds them at the requisite angle to direct the collimated light from lamp 28 upwardly through the long leg portion 20 of duct 16 on the one side and the short leg portion 18 of duct 16 and duct 24 on the other side.

Photoelectric cells 34 and 38 are photoresistive cells,

which, for example, may be RCA Model No. 7163, and

are mounted on a circuit board 50. The circuit board also contains a potentiometer 52 and terminals 54 for connection to a recorder readout device as will be described hereinafter. A source of power for the circuit board may be a l2-volt battery 64 or other suitable dc or ac power supply. The lamp 28 is connected to a source of ac voltage 58, one side of which is grounded to the housing as at 60. The other side of the ac voltage source 58 leads to a contact at the base of the bulb 28.

The electrical system of the detector of the invention is basically a simple Wheatstone bridge using photoelectric cells 34 and 38 as two arms of the bridge and potentiometer 52 as the other two arms of the bridge disposed on either side of its sliding contact 61. These components are mounted on or attached to the circuit board 50.

Photoelectric cells 34 and 38 are set into the top of open-ended collimating tubes 34a and 38a, respectively. The collimating tubes 34a and 38a keep stray illumination from affecting the photoelectric cells and restrict their view entirely to the collimated beams coming up from the mirrors 32 and 36. Collimating tubes 34a and 38a may be attached to the circuit board 50 by mounting straps 62 and held at a spacing which corresponds to the center line spacing of the long leg portion 20 of duct 16 on one side and the center line of the aligned short leg portion 18 of duct 16 and duct 24 on the other side.

A recorder readout device 66 which may be, for example, a potentiometer recorder, Speedomax H, Model R manufactured by Leeds & Northrup Company, is connected with terminals 54. The entire device is powered by either the battery 64 or other power supply which, for example, could be Model No. LCS-3-O2 manufactured by the Lambda Corporation. The recorder readout device 66 is attached to the terminals 54, and power supply 64 is connected to the Wheatstone bridge as shown.

In operation, the housing 10 is installed by inserting it through the aperture 4 in such a manner that the long leg portion 20 of duct 16 is protected from the smoke or particulate matter in the flue. However, the short leg end portion 18 of duct 16 is open at its end which end is aligned with but spaced from the open end 26 of duct 24 so that particulate matter and smoke will pass between these two open ends and interrupt the light beam that passes through the end portion 18 of the duct 16 and the duct 24. The lamp 28 directs equivalent beams of light at the two mirrors 32 and 36 and which beams of light impinge upon the photoelectric cells 34 and 38, respectively. If there is no smoke between the open ends of the ducts l6 and 24, the paths of light between the mirrors 32 and 36 and the photoelectric cells 34 and 38, respectively, are equally clear. In this case each photoelectric cell receives the same amount of light and the potentiometer 52 is adjusted so that the bridge is in balance and there is no output on terminals 54. If smoke or particulate matter enters the space between the end 18 of duct 16 and the end 26 of duct 24, photoelectric cell 34 will increase in resistance and unbalance the bridge to a degree proportional to its increase in resistance. The unbalance will be sensed as a voltage at terminals 54 and will be displayed on the recorder 66. Resistance values of photoelectric cells 34 and 38 and potentiometer 52 are chosen to make the recorder 66 go from zero to full scale at an arbitrary range of smoke densities in the space between the duct ends 18 and 26.

It will be noted that an important advantage of my invention is that a differential clouding of mirrors 32 and 36 as dirt is deposited on them may be compensated for by adjustment of potentiometer 52 when it is known that clean gas is in the space between the duct ends 18 and 26. i

Another important feature of my invention is the arrangement whereby the lamp compartment 12, the lenses 30 and the mirrors 32 and 36 are kept cool and clean. The temperature within the flue may approach 900 to lOOOF and the pressure in the flue will generally be in the order of one inch water column below the ambient atmospheric pressure outside the duct. The arrangement of my invention is designed so that compartment 12 is cooled by ambient air drawn in through apertures 40 in duct 22 down the annular space between duct 16 and duct 22 around the right angle that surrounds the compartment 12 and out the opening 42 which is adjacent the inner end of the duct 22 within the flue. Thus ambient air is constantly washed down and around duct 16, compartment 12 and duct 24. Arrows indicate the flow of ambient cooling air through duct 16. An additional flow of ambient air is realized through ducts 16 and 24. Since the short leg end of duct 16 terminates with an open end 18 to the interior of the main flue and the duct 24 also terminates with an opening to the interior of the main flue, through which gas is flowing at a lower than atmospheric pressure, air is drawn out of the open ends 18 and 26 and must necessarily come down ducts l6 and 24. The air coming down through duct 16 passes through the lamp housing to get to the open end of short portion 18. This air is drawn in under the loose cover 46 and into the compartment 14 through the filter 44, then it sweeps down through the long leg 20 of duct 16 across mirrors 32 and 36, and lamp 28, and discharges into the flue from the open end of the short leg portion 18 of duct -16. This flow of air helps to keep photoelectric cell 38,

the mirrors 32 and 36 and lenses 30 a and 30b clean and cool. An additional flow of air sweeps down through the duct 24 and helps to keep the photoelectric cell 34 clean and cool. The ambient air which passes down through the ducts l6 and 24 is filtered by the filter 44 to keep it clean as possible.

The relatively long straight arrows in the compartment-l2 and long leg of duct 16 and in duct 24 indicate the direction of light travel in the device of the invention.

It will be recognized that I have described but one embodiment of my invention. 1 have, for example, cited a simple Wheatstone bridge that is read out by a potentiometer recorder. The recorder readout device might well be a galvanometer type instrument, such as a simple panel meter, either directly connected to terminals 54 or connected through an operational amplifier that may be used to adjust the impedances in the bridge system. It will be apparent that the power supply 64-can be any source of dc or ac voltage. I have chosen do in this embodiment to simplify the readout of the bridge.

It will also be noted that voltage source 64 and recorder 66 may be located at any distance from the instrument compartment 14 or may be embodied within the compartment 14 itself. The embodiment l have shown has them separated from the compartment 14. It should also be noted that the voltage source 58 that supplies the lamp 28 may be of any.voltage convenient to supply light of-sufficient intensity to activate photoelectric cells 34 and 38 through the required range of their readings. r

If desired, theduct 22 may be omitted where cooling means are not required or desired, as for example, when theapparatus of the invention is to be used to measure particulate matter in low temperature gas.

It should now be apparent that the apparatus of the invention consists of a device that can be inserted into one opening of a smoke-filled flue and function effectively to detect particulate matter in the gas within the flue. It should also be apparent that the apparatus of the invention provides a smoke detector or particulate matter detector that is integrally cooled and makes use of the pressure differential between the gas flowing through the flue and the ambient airoutside the flue to provide a motive force for circulating cooling and cleaning air. The arrangement of the invention also provides a system of filters and ducts that keep clean filtered air passing through the lamp and mirror compartment to cool and clean the same.

If the pressure in the smoke-filled flue is higher than the ambient atmospheric pressure outside the appara-.

ms of the invention, a blower (not shown) may be used to supply motive force to circulate ambient air through ducts 16, 22 and 24.

While 1 have shown but one embodiment of my invention, other adaptations and modifications may be made without departing from the scope of the following claims.

-[ claim:

1. Apparatus for detecting particulate matter in a gas stream flowing through a gas passageway having a lateral opening intermediate its ends which comprises an elongated housing adapted to be disposed transversely in said passageway through said opening with one end thereof projecting from said passageway outwardly of said opening, means surrounding said'housing sealing said opening, a first compartment in the end of said housing adapted to be inserted into said passageway, a second compartment at the opposite end of said housing normally disposed outside of said passageway when said housing is inserted therein, a first duct in said housing connected with said compartments, said first duct being substantially L-shape and having an open-end short leg portion extending from said first compartment substantially parallel with the long leg portion of said L-shape first duct,a substantially L-shape sleeve concentrically surrounding said first L-s hape duct substantially along its length, a second duct extending from said second compartment toward said open end of said first duct in spaced alignment therewith, a light source in said first compartment, a first photoelectric cell in said second compartment aligned with said first duct, a second photoelectric cell in said second compartment aligned with said second duct and with the open end of said first duct, means in said first compartment directing light from said light source to said first and second photoelectric cells, and means connected with said photoelectric cells adapted to indicate differences in the intensity of light reaching said first and second photoelectric cells from said light source thereby indicating whether particulate matter is present in the gas stream in the passageway between the open ends of said first and second ducts.

2. Apparatus for detecting particulate matter in a gas stream flowing through a gas passageway at a pressure lower than atmospheric pressure having a lateral'opening intermediate its ends which comprises an elongated housing adapted to be disposed transversely in said pas sageway through said opening with one end thereof projecting from said passageway outwardly of said opening, means surrounding said .housing sealing said opening, a first compartmentin the end of said housing adapted to be inserted into said passageway, a second compartment at the opposite end of said housing nor mally disposed outside of said passageway when said housing is inserted therein, a first duct in said housing connected with said compartment, said first duct being substantially L-shape and having an open-end short leg portion extending from said first compartment substantially parallel with the long leg portion of said L-shape first duct, a substantially L-shape sleeve concentrically surrounding said first L-shape duct substantially along its length, a second duct substantially surrounding and concentric with said first duct, a third duct having an open end extending from said second compartment into said passageway toward said open end of said first duct in spaced alignment therewith, said second compartment and said second duct having openings for circulation of ambient air through said ducts from the atmosphere outside said passageway into said passageway, a light source in said first compartment, a first photoelectric cell in said second compartment aligned with said first duct, a second photoelectric cell in said second compartment aligned with said third duct and with the open end of said first duct, means in said first compartment directing light from said light source to said first and second photoelectric cells, and means connected with said photoelectric cells adapted to indicate differences in the intensity of light reaching said first and second photoelectric cells from said light source thereby indicating whether particulate matter is present in the gas stream in the passageway between said third duct and said open-end short leg portion of said first duct.

3. Apparatus as defined by claim 2 in which the pressure of said gas'stream is above atmospheric pressure, and a air-circulation-inducing means is disposed in said housing.

4. Apparatus as defined by claim 2 in which an air filter is disposed in the path of ambient air flowing through said air openings in said second compartment to said first and third ducts. 

1. Apparatus for detecting particulate matter in a gas stream flowing through a gas passageway having a lateral opening intermediate its ends which comprises an elongated housing adapted to be disposed transversely in said passageway through said opening with one end thereof projecting from said passageway outwardly of said opening, means surrounding said housing sealing said opening, a first compartment in the end of said housing adapted to be inserted into said passageway, a second compartment at the opposite end of said housing normally disposed outside of said passageway when said housing is inserted therein, a first duct in said housing connected with said compartments, said first duct being substantially L-shape and having an open-end short leg portion extending from said first compartment substantially parallel with the long leg portion of said L-shape first duct, a substantially L-shape sleeve concentrically surrounding said first L-shape duct substantially along its length, a second duct extending from said second compartment toward said open end of said first duct in spaced alignment therewith, a light source in said first compartment, a first photoelectric cell in said second compartment aligned with said first duct, a second photoelectric cell in said second compartment aligned with said second duct and with the open end of said first duct, means in said first compartment directing light from said light source to said first and second photoelectric cells, and means connected with said photoelectric cells adapted to indicate differences in the intensity of light reaching said first and second photoelectric cells from said light source thereby indicating whether particulate matter is present in the gas stream in the passageway between the open ends of said first and second ducts.
 2. Apparatus for detecting particulate matter in a gas stream flowing through a gas passageway at a pressure lower than atmospheric pressure having a lateral opening intermediate its ends which comprises an elongated housing adapted to be disposed transversely in said passageway through said opening with one end thereof projecting from said passageway outwardly of said opening, means surrounding said housing sealing said opening, a first compartment in the end of said housing adapted to be inserted into said passageway, a second compartment at the opposite end of said housing normally disposed outside of said passageway when said housing is inserted therein, a first duct in said housing connected with said compartment, said first duct being substantially L-shape and having an open-end short leg portion extending from said first comPartment substantially parallel with the long leg portion of said L-shape first duct, a substantially L-shape sleeve concentrically surrounding said first L-shape duct substantially along its length, a second duct substantially surrounding and concentric with said first duct, a third duct having an open end extending from said second compartment into said passageway toward said open end of said first duct in spaced alignment therewith, said second compartment and said second duct having openings for circulation of ambient air through said ducts from the atmosphere outside said passageway into said passageway, a light source in said first compartment, a first photoelectric cell in said second compartment aligned with said first duct, a second photoelectric cell in said second compartment aligned with said third duct and with the open end of said first duct, means in said first compartment directing light from said light source to said first and second photoelectric cells, and means connected with said photoelectric cells adapted to indicate differences in the intensity of light reaching said first and second photoelectric cells from said light source thereby indicating whether particulate matter is present in the gas stream in the passageway between said third duct and said open-end short leg portion of said first duct.
 3. Apparatus as defined by claim 2 in which the pressure of said gas stream is above atmospheric pressure, and a air-circulation-inducing means is disposed in said housing.
 4. Apparatus as defined by claim 2 in which an air filter is disposed in the path of ambient air flowing through said air openings in said second compartment to said first and third ducts. 